1. Field
The present disclosure relates generally to a method and system for measuring the air mass flow into an inlet of a compressor section of a gas turbine engine, and more particularly, to a method and system for measuring the total air mass flow into the inlet of a compressor section of a gas turbine engine.
2. Description of the Related Art
In a turbomachine, such as a gas turbine engine, air is pressurized in a compressor section then mixed with fuel and burned in a combustion section to generate hot combustion gases. The hot combustion gases are expanded within a turbine section of the engine where energy is extracted from the combustion gases to power the compressor section to produce useful work, such as turning a generator to produce electricity.
Air mass flow is a key measurement of determining the efficiency of a gas turbine. This quantity is difficult to measure accurately because the most accurate measurement methods themselves create an impedance to air flow, which significantly reduces the power produced by the engine. Other techniques have proven extremely expensive, inaccurate, or accurate but requiring a large configuration space.
One such conventional method of accurately measuring air mass flow into a large gas turbine is to use a large array of large nozzles. The flow nozzles have a very low impedance and thus can provide an accurate measurement of the air mass flow. However, using a flow nozzle requires ample space to accommodate its setup requirements and is very expensive. Additionally, the relatively high pressure drop across the flow nozzle reduces the power output of the engine.
Another conventional method frequently used, commonly referred to as the Scroll dP method, estimates the air mass flow of the gas turbine by a formula using the output performance of the system, fuel parameters, the difference between the compressor intake barometric pressure at the compressor inlet and the static pressure at the throat of the inlet scroll and intake air temperature. While the estimate is fairly accurate when used for high load operation, it not consistently accurate under all load conditions. Additionally, this method only gives a mass flow estimate for performance evaluation and is not useful for monitoring the flow distribution in the air intake. Thus, it cannot be used to optimize the flow performance of the air intake locally.
An accurate and inexpensive method to measure air mass flow at the inlet to a compressor section of a gas turbine engine is desired.